The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, the aortic wall can weaken, resulting in an aneurysm. Upon further exposure to hemodynamic forces, such an aneurysm can rupture.
One surgical intervention for weakened, aneurysmal, or ruptured vessels involves the use of a prosthetic device or prosthesis to provide some or all of the functionality of the original, healthy vessel, and/or preserve any remaining vascular integrity by replacing a length of the existing vessel wall that spans the site of vessel failure. For example, techniques have been developed for repairing abdominal aortic aneurysms by intraluminally delivering an endovascular graft to the aneurysm site through the use of a catheter-based delivery system. The endovascular grafts typically include a tube of pliable material (e.g., expanded polytetrafluoroethylene (ePTFE) or woven polyester) in combination with a graft anchoring component, which operates to hold the tubular graft in its intended position within the aorta. Most commonly, the graft anchoring component is formed of a stent or frame that is radially expandable to exert outwardly directing radial pressure against the surrounding blood vessel wall. The stent or frame can be either attached to or incorporated into the body of the tubular graft or provided separate from the graft and deployed within the graft.
It is preferable that these prostheses seal off the failed portion of the vessel. For weakened or aneurysmal vessels, even a small leak in the prosthesis may lead to the pressurization of, or flow in, the treated vessel which may aggravate the condition the prosthesis was intended to treat. A prosthesis of this type may be used, for example, to treat aneurysms of the abdominal aortic, iliac, or branch vessels, such as the renal, arteries.
A prosthetic device may be of unitary construction or may include multiple prosthetic modules. Modular systems typically are assembled in situ by overlapping the tubular ends of the prosthetic modules so that the end of one module sits partially inside the other module, preferably forming circumferential apposition through the overlap region. This attachment process is called “tromboning.” The connections between prosthetic modules are typically maintained by the frictional forces at the overlap region and enhanced by the radial force exerted by the internal prosthetic module on the external prosthetic module where the two overlap. The fit may be further enhanced by stents fixed to the modules at the overlap region.
A prosthetic device including multiple prosthetic modules may be used for placement at a bifurcation or branch of the vasculature. In the case of a bifurcation, one module may be placed in the primary body vessel and one leg of the bifurcation, and another module may be placed in the other leg of the bifurcation. In the case of a branch, one module may be placed in the primary body vessel, and another module may be placed in the branch vessel. Multiple delivery devices may be used to place the different modules used to form the prosthetic device.
In some situations, a bifurcated or branched graft may be mated with an extension graft. For example, a bifurcated graft may be placed at the bifurcation of the common iliac artery into the external iliac artery and the internal iliac artery to treat an iliac aneurysm. The bifurcated graft may include a main pathway for the external iliac artery and a side branch for the internal iliac artery. The bifurcated graft may be mated to an extension graft overlapping a portion of the bifurcated graft, and the overlap may be disposed proximal of the side branch and within the common iliac artery. If the common iliac artery is especially short, there may not be sufficient space for the bifurcated graft and the extension graft to seal properly. Moreover, shortening the overlap between the bifurcated graft and the extension graft may increase the likelihood of type III endoleak or complete separation of the prosthetic device.